Sacroiliac fusion system

ABSTRACT

An undercutting system for preparing a region between ilium and sacrum for sacroiliac fusion. The undercutting system includes an insertion apparatus and a cutting assembly. The insertion apparatus has an elongate shaft and a rotatable handle. The cutting assembly is operably attached to the insertion apparatus. Rotation of the handle with respect to the shaft causes the cutting assembly to move with respect to the shaft between a retracted configuration and an extended configuration. When in the extended configuration, at least a portion of the cutting assembly extends laterally from the shaft.

REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.12/938,976, which was filed on Nov. 3, 2010, and this application claimspriority to U.S. Provisional Application No. 61/292,021, which was filedon Jan. 4, 2010, the contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

An embodiment of the invention is directed to a system for treatingpatients experiencing sacroiliac joint pain. More particularly, theinvention relates to a system for preparing a space between the sacrumand the iliac to facilitate sacroiliac joint fusion.

BACKGROUND OF THE INVENTION

The sacroiliac joint is located at the intersection of the ilium, theupper bone of the pelvis, and the sacrum at the base of the spine. Oneof the primary functions of the sacroiliac joint is to provide shockabsorption of pressures put on the spine.

Certain persons experience pain in the sacroiliac joint. This pain mayresult from a variety of causes, examples of which include injuries,incorrect vertebra fusion during pre-birth development and effects ofpregnancy.

If initial efforts to reduce the pain in the sacroiliac joint throughphysical therapy and/or steroid injections are not effective, surgerymay be needed to fuse together the sacroiliac joint. One typicalsurgical technique involves forming an incision in the lower back overthe sacroiliac joint. The articular cartilage is removed from bothsurfaces. This process is also called chondrectomy.

The sacrum and the ilium are held together with screws or a plate.Eventually, bone grows between the sacrum and the ilium to thereby fusetogether the sacroiliac joint. Because of the challenges in accessingthe surfaces of the sacrum and the ilium that will fuse together, thistype of surgery may result in damage to tissue, nerves and/or bloodvessels that surround the sacroiliac joint. Such damage may prevent thepatient from fully realizing the benefits of the sacroiliac joint fusionand in some instances cause the patient to experience more pain afterthe sacroiliac joint fusion than before the sacroiliac joint fusion.

SUMMARY OF THE INVENTION

An embodiment of the invention is directed to an undercutting system forpreparing a region between an ilium and an sacrum for sacroiliac fusion.The undercutting system includes an insertion apparatus and cuttingassembly.

The insertion apparatus having an elongate shaft and a rotatable handle.The cutting assembly is operably attached to the insertion apparatus.Rotation of the handle with respect to the shaft causes the cuttingassembly to move with respect to the shaft between a retractedconfiguration and an extended configuration. When in the extendedconfiguration, at least a portion of the cutting assembly extendslaterally from the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 is a perspective view of an undercutting system for use in asacroiliac fusion procedure.

FIG. 2 is a side view of the undercutting system of FIG. 1.

FIG. 3 is a first end view of the undercutting system of FIG. 1.

FIG. 4 is a second end view of the undercutting system of FIG. 1.

FIG. 5 is a sectional view of the sacroiliac joint with an apertureformed in the ilium.

FIG. 6 is a perspective view of an end portion of a probe assembly foruse with the undercutting system.

FIG. 7 is a top view of the end portion of the probe assembly of FIG. 6.

FIG. 8 is a side view of the end portion of the probe assembly of FIG.6.

FIG. 9 is an end view of the end portion of the probe assembly of FIG.6.

FIG. 10 is a perspective view of an end portion of a first cuttingassembly for use with the undercutting system.

FIG. 11 is a top view of the end portion of the first cutting assemblyof FIG. 10.

FIG. 12 is a side view of the end portion of the first cutting assemblyof FIG. 10.

FIG. 13 is an end view of the end portion of the first cutting assemblyof FIG. 10.

FIG. 14 is a perspective view of an end portion of a cutting assemblyfor use with the undercutting system.

FIG. 15 is a top view of the end portion of the cutting assembly of FIG.14.

FIG. 16 is a side view of the end portion of the cutting assembly ofFIG. 14.

FIG. 17 is an end view of the end portion of the cutting assembly ofFIG. 14.

FIG. 18 is a sectional view of an undercutting system for use inconjunction with sacroiliac fusion in a partially extendedconfiguration.

FIG. 19 is a sectional view of the undercutting system of FIG. 18positioned adjacent to an undercutting guide that has been inserted intothe aperture formed in the ilium where a cutting assembly is in aretracted configuration.

FIG. 20 is a sectional view of the undercutting system of FIG. 18positioned between the sacrum and the ilium where the cutting assemblyis in an extended configuration.

FIG. 21 is an end view of the cutting assembly of FIG. 18 when in theextended configuration.

FIG. 22 is a perspective view of a cutting assembly of FIG. 18.

FIG. 23 is an alternative configuration of a cutting head for theundercutting system of FIG. 18.

FIG. 24 is an alternative configuration of a cutting head for theundercutting system of FIG. 18.

FIG. 25 is an alternative configuration of a cutting head for theundercutting system of FIG. 2.

FIG. 26 is a sectional view of an alternative undercutting systempositioned adjacent to an undercutting guide that has been inserted intothe aperture formed in the ilium.

FIG. 27 is a side view of a cutting assembly for the undercutting systemof FIG. 26.

FIG. 28 is a top view of the cutting assembly of FIG. 27.

FIG. 29 is a side view of a link for the cutting assembly of FIG. 27.

FIG. 30 is a side view of an alternative configuration of the cuttingassembly for undercutting system of FIG. 28.

FIG. 31 is a top view of the cutting assembly of FIG. 30.

FIG. 32 is a side view of a link for the cutting assembly of FIG. 30.

FIG. 33 is a side view of another configuration of the cutting assemblyfor the undercutting system of FIG. 26.

FIG. 34 is a top view of the cutting assembly of FIG. 33.

FIG. 35 is a top view of an alternative configuration of the cuttingassembly of FIG. 33.

FIG. 36 is a perspective view of an alternative configuration of thecutting assembly for the undercutting system of FIG. 26.

FIG. 37 is a side view of an alternative configuration of the cuttingassembly for the undercutting system of FIG. 26.

FIG. 38 is a sectional view of an alternative undercutting systempositioned adjacent to an undercutting guide that has been inserted intothe aperture formed in the ilium.

FIG. 39 is an end view of a cutting head for the undercutting system ofFIG. 38 where the cutting head is in a retracted position.

FIG. 40 is an end view of the cutting head for the undercutting systemof FIG. 38 where the cutting head is in an extended position.

FIG. 41 is a perspective view of a cutting arm for use on the cuttinghead illustrated in FIGS. 39 and 40.

FIG. 42 is a perspective view of an alternative configuration of acutting arm for use on the cutting head illustrated in FIGS. 39 and 40.

FIG. 43 is a perspective view of an alternative configuration of acutting arm for use on the cutting head illustrated in FIGS. 39 and 40.

FIG. 44 is a perspective view of an alternative configuration of acutting arm for use on the cutting head illustrated in FIGS. 39 and 40.

FIG. 45 is a sectional view of an alternative undercutting systempositioned adjacent to an undercutting guide that has been inserted intothe aperture formed in the ilium.

FIG. 46 is a sectional view of an alternative undercutting systeminserted into the aperture formed in the ilium where a cutting head isin a retracted position.

FIG. 47 is a sectional view of the undercutting system of FIG. 42 wherethe cutting head is in an extended position.

FIG. 48 is a side view of the cutting head of FIGS. 46 and 47 in a firstarticulated position.

FIG. 49 is a side view of the cutting head of FIGS. 46 and 47 in asecond articulated position.

FIG. 50 is a sectional view of another alternative undercutting systempositioned adjacent to an undercutting guide that has been inserted intothe aperture formed in the ilium where a cutting head is in a retractedposition.

FIG. 51 is a perspective view of the undercutting system of FIG. 50where the cutting head is in an extended position.

FIG. 52 is a side view of an alternative configuration of the cuttinghead for the undercutting system of FIG. 50.

FIG. 53 is a side view of an alternative configuration of theundercutting system where the undercutting system is in a refractedconfiguration.

FIG. 54 is a side view of the undercutting system of FIG. 53 that hasbeen inserted into an aperture formed in the ilium where theundercutting system is in an extended configuration.

FIG. 55 is a side view of an alternative configuration of theundercutting system.

FIG. 56 is a top view of the aperture in the ilium for use with theundercutting system of FIG. 55.

FIG. 57 is a sectional view of an alternative configuration of theundercutting system.

FIG. 58 is a sectional view of an alternative configuration of theundercutting system.

FIG. 59 is a sectional view of an alternative configuration of theundercutting system.

FIG. 60 is a top view of an alternative configuration of theundercutting system.

FIG. 61 is a top view of an alternative configuration of theundercutting system.

FIG. 62 is a sectional view of an alternative configuration of theundercutting system.

FIG. 63 is an end view of the undercutting system of FIG. 62.

FIG. 64 is a side view of an alternative configuration of theundercutting system in a refracted configuration.

FIG. 65 is a side view of the undercutting system of FIG. 63 in anextended configuration.

FIG. 66 is a sectional view of an alternative configuration of theundercutting system.

FIG. 67 is an end view of a cutting head for use with the undercuttingsystem of FIG. 66.

FIG. 68 is an end view of another cutting head for use with theundercutting system of FIG. 67.

FIG. 69 is an end view of another cutting head for use with theundercutting system of FIG. 67.

FIG. 70 is a sectional view of an alternative configuration of theundercutting system where the undercutting system is in a retractedconfiguration.

FIG. 71 is a sectional view of the undercutting system of FIG. 70 wherethe undercutting system is in an extended configuration.

FIG. 72 is a sectional view of an alternative configuration of theundercutting system where the undercutting system is in a retractedconfiguration.

FIG. 73 is a sectional view of the undercutting system of FIG. 72 wherethe undercutting system is in an extended configuration.

FIG. 74 is a perspective view of an alternative configuration of theundercutting system where a cutting assembly is in an extendedconfiguration.

FIG. 75 is a sectional view of the undercutting system of FIG. 74.

FIG. 76 is a sectional view of an alternative configuration of theundercutting system where a cutting assembly is in a retractedconfiguration.

FIG. 77 is a side view of a cutting assembly guide for the undercuttingsystem of FIG. 76.

FIG. 78 is a side view of a connector head for the undercutting systemof FIG. 76.

FIG. 79 is a side view of an advancement handle for the undercuttingsystem of FIG. 76.

FIG. 80 is a side view of a cutting assembly for the undercutting systemof FIG. 76.

FIG. 81 is a side view of a rotation handle for the undercutting systemof FIG. 76.

FIG. 82 is a sectional view of an alternative configuration of theundercutting system where a cutting assembly is in an extendedconfiguration.

FIG. 83 is a sectional view of an alternative configuration of theundercutting system where a cutting assembly is in an extendedconfiguration.

FIG. 84 is a sectional view of an alternative configuration of theundercutting system where a cutting assembly is in an extendedconfiguration.

FIG. 85 is a sectional view of a guide head for use on the cuttingassembly of FIG. 84.

FIG. 86 is an end view of the undercutting system of FIG. 84.

FIG. 87 is a top view of an alternative aperture configuration formed inthe ilium.

FIG. 88 is a top view of an undercutting system used in conjunction withthe aperture of FIG. 87.

FIG. 89 is a partially cut away perspective view of an aperture beingdrilled in the sacrum and the ilium as an initial step in a sacroiliacfusion procedure.

FIG. 90 is a partially cut away perspective view of an undercuttingsystem being inserted into the aperture.

FIG. 91 is a partially cut away perspective view of the undercuttingsystem being used to form an undercut region between the sacrum and theilium.

FIG. 92 is a partially cut away perspective view of fasteners insertedinto the apertures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention is directed to an undercutting system 30for preparing surfaces of the ilium and the sacrum for sacroiliac jointfusion, such as is illustrated in FIGS. 1-4. The undercutting systemutilizes an aperture 10 formed in the ilium 14 to access a region 12between the ilium 14 and the sacrum 16, as illustrated in FIG. 5.

In certain embodiments, the aperture 10 may have a diameter of up toabout 50 millimeters. In other embodiments, the aperture 10 may have adiameter of between about 6 millimeters and 20 millimeters.

The undercutting system thereby enables tissue such as cartilage to beremoved from the adjacent surfaces of the ilium 14 and the sacrum 16.This procedure may be referred to as preparing bleeding bone surfaces onthe ilium 14 and the sacrum 16, which are more receptive to growing bonebetween them as part of sacroiliac joint fusion. Thereafter, the ilium14 and the sacrum 16 may be held in a stationary position with respectto each other so that bone may grow between the ilium 14 and the sacrum16 to thereby fuse the sacroiliac joint.

Performing the sacroiliac fusion using the undercutting system 30disclosed herein reduces the complexity of the sacroiliac fusion whencompared to prior techniques used for sacroiliac fusion. Additionally,sacroiliac fusion performed using the concepts describe herein has thepotential of fewer side effects because it does not require the surgeonto work proximate the nerves and/or blood vessels, as is done with priorsacroiliac fusion techniques.

Furthermore, the apparatus and technique disclosed herein does notformally expose the sacroiliac joint to reduce the potential ofinfection. The time associated with preparing the surfaces of the iliumand the sacrum is also reduced when compared to the prior more invasivetechniques used to prepare the joint for fusion.

In one embodiment, the undercutting system 30, may include a cuttingassembly 32 that is operably mounted with respect to an insertionapparatus 34, as illustrated in FIGS. 1-4. The cutting assembly 32 mayhave a U-shaped configuration where the ends of the cutting assembly 32are operably attached to the insertion apparatus 34.

The configuration of the cutting assembly 32 provides the cuttingassembly 32 with sufficient rigidity in a radial direction. Such aconfiguration allows the cutting assembly 32 to resist deformation inresponse to rotation of the undercutting system 30 during the cuttingprocess such as when the tissue between the ilium 14 and the sacrum 16is contacted with the cutting assembly 32.

The configuration of the cutting assembly 32 also provides the cuttingassembly 32 with flexibility in a distal-proximal direction. Such aconfiguration allows the cutting assembly 32 to deflect in response toencountering resistance in the distal-proximal direction. The resistanceenables the cutting assembly 32 to deflect in response to changes in theshape or orientation of the ilium 14 or the sacrum 16. Such deflectionis important because it is much more difficult to cut through the boneof the ilium 14 and the sacrum 16 than the cartilage that is between theilium 14 and the sacrum 16.

The cutting assembly 32 may be formed with a length that is no greaterthan a diameter of the elongated shaft 50. Forming the cutting assembly32 with such a configuration enables the cutting assembly 32 to bepositioned substantially within a profile of the elongated shaft 50 whenthe cutting assembly 32 is in a retracted configuration so that thecutting assembly 32 does not interfere with the insertion of the toolthrough the aperture in the ilium 14.

The cutting assembly 32 may include a cutting surface 38 on at least oneedge thereof. In certain embodiments, cutting surfaces 38 are providedon the upper and lower edges on both sides of the cutting assembly 32.Providing the cutting surfaces 38 on these edges enables the cuttingassembly 32 to cut while being rotated in clockwise and counterclockwise directions. Providing the cutting surfaces 38 on these edgesalso enables the cutting assembly 32 to cut on the ilium 14 and thesacrum 16 sides of the cutting assembly 32.

In certain embodiments, a distal end 40 of the cutting assembly 32 doesnot have a cutting surface on the edges thereof. Forming the distal end40 with cutting surfaces on the edges thereof enables the cuttingassembly to resist cutting too strongly into the ilium 14, the sacrum 16or the cartilage between the ilium 14 and the sacrum 16.

The insertion apparatus 34 may include an elongated shaft 50 that isformed with a length that enables a proximal end thereof to be positionoutside of the patient's body while a distal end thereof is utilized tothe prepare the region between the ilium 14 and the sacrum 16 for thefusion process. In certain embodiments, the length of the elongatedshaft 50 is between about 6 inches and about 18 inches.

The elongated shaft 50 may be formed with a relatively small outerdiameter to reduce a size of the aperture that is formed in the ilium14. The larger the aperture that is formed in the ilium 14, the greaterthe potential of the aperture weakening to the point at which the ilium14 is more susceptible to breakage. In certain embodiments, the outerdiameter of the elongated shaft 50 is between about 6 millimeters and 20millimeters.

The insertion apparatus 34 may include a control portion 52 thatfacilitates extension and retraction of the cutting assembly 32 as wellas rotation of the cutting assembly 32. In certain embodiments, theextension and retraction of the cutting assembly 32 are controlledutilizing a plate 60 and a handle 62 that is operably mounted withrespect to the plate.

The plate 60 may have a generally circular configuration, as mostclearly illustrated in FIG. 3. An outer edge of the plate 60 may have aplurality of recesses 64 formed therein that enhance a person's abilityto grasp the plate 60 to either maintain the plate 60 in a desiredposition or to rotate the plate 60. The recesses 64 may each have aconcave configuration.

The plate 60 may include a plurality of recesses 66 formed in an uppersurface thereof. The recesses 66 extend at least partially between theupper surface and the lower surface of the plate. The recesses 66 may beoriented in a semi-circular configuration about an axis. This axis maybe offset from a central axis of the plate 60.

A spacing between at least some of the adjacent recesses 66 may besubstantially equal. On the other hand, the spacing between adjacentrecesses 66 may get progressively larger, as illustrated in FIG. 3.

The handle 62 may be rotatable mounted to the plate 60 for rotationabout an axis that is the same as the axis about which the semi-circularconfiguration of the recesses 66 is oriented. Rotation of the handle 62causes the cutting assembly 32 to be rotated with respect to theelongated shaft 50 to move the cutting assembly 32 between an extendedconfiguration and a retracted configuration depending on which directionthe handle 62 is rotated.

The handle 62 may be operably connected to the cutting assembly 32 suchthat rotation of the handle 62 causes rotation of the cutting assembly32. One potential mechanism for operably connecting the handle 62 andthe cutting assembly 32 is a shaft (not shown) that extends between thehandle 62 and the cutting assembly 32.

The shaft may be rotatable about an axis that is offset from a centralaxis of the elongated shaft 50. Mounting the shaft in this mannerenables the cutting assembly 32 to be fabricated with a length that isapproximately the same as a diameter of the elongated shaft 50. Thisconfiguration thereby allows the cartilage to be removed from a largerarea between the ilium 14 and the sacrum 16 to increase the likelihoodthat the fusion process will be successful by increasing the area of thefusion between the ilium 14 and the sacrum 16.

It is also possible to include at least one gear between the handle 62and the cutting assembly 32. The at least one gear may either decreaseor increase the amount of movement of the cutting assembly 32 inresponse to a specified movement of the handle 62.

A locking pin 70 may be operably connected to the handle 62 for movementbetween a locked configuration and an unlocked configuration. When inthe locked configuration, the locking pin 70 extends at least partiallyinto one of the recesses 66 to thereby retain the handle 62 in a fixedposition with respect to the plate 60. When in the unlockedconfiguration, the locking pin 70 does not extend into the recess 66,which enables the handle 62 to be rotated with respect to the plate 60for extending or retracting the cutting assembly 32 from the elongatedshaft 50.

The locking pin 70 may be biased to the locked configuration to preventinadvertent rotation of the handle 62 to thereby cause unintendedextension or retraction of the cutting assembly 32.

A gripping mechanism 72 may be operably attached to the locking pin 70.The gripping mechanism 72 may have a diameter that is great than adiameter of the locking pin 70. The gripping mechanism 72 therebyenhances the ability to move the locking pin 70 from the lockedconfiguration to the unlocked configuration.

The insertion apparatus 34 may also include a rotation control mechanism80 to facilitate rotation of the cutting assembly 32. In certainembodiments, the rotation control mechanism 80 has a generally circularconfiguration. A diameter of the rotation control mechanism 80 may begreater than a diameter of the plate 60. Such a configuration enablesthe rotation control mechanism 80 to be grasped separately from theplate 60.

A lock mechanism 82 may be provided on the insertion apparatus 34 toprevent rotation of the rotation control mechanism 80. At least one arm84 may extend radially outward from elongated shaft 50 to facilitateattachment of the lock mechanism 82 to the insertion apparatus 34. Thearm 84 may have a length that is greater than a length of the radius ofthe rotation control mechanism 80.

The lock mechanism 82 may be rotatably mounted to the arm 84. Rotationof the lock mechanism 82 with respect to the arm 84 causes a distancebetween the lock mechanism 82 and the arm 84 to be reduced such thatthere is frictional contact between the lock mechanism 82 and therotation control mechanism 80. In certain embodiments, there may also befrictional contact between the arm 84 and the rotation control mechanism80 when the lock mechanism 80 is in the locked configuration.

In one embodiment of the undercutting system, at least two differentcutting assemblies are utilized to prepare the sacroiliac joint forfusion. Using more than one assembly to prepare the sacroiliac jointfusion enhances the accuracy of the preparation process. In such aprocess, a first cutting assembly 132 (FIGS. 6-9) is used as a probe todefine the general region where the sacroiliac joint fusion will takeplace. A second cutting assembly 232 (FIGS. 10-13) is then used to cut amajority of the tissue from where the sacroiliac joint fusion will takeplace. A third cutting assembly 332 (FIGS. 14-17) is next used to scrapethe bone surfaces where the sacroiliac joint fusion will take place.

As the first cutting assembly 132 is used to define the general regionwhere the sacroiliac fusion will take place, the first cutting assembly132 may be formed with a distal tip 140 that does not include providinga significant cutting action. Rather, the distal tip 140 may have atapered configuration where a width and a height proximate a distal endthereof is less than a width and a height of the plurality of links 150.The tapered configuration enhances the ability of the distal tip 140 toextend through the tissue as opposed to the distal tip 140 having anon-tapered end.

Rather than being sharpened to facilitate cutting into the tissuebetween the sacrum and the ilium, side edges and a distal end of thedistal tip 140 may curved. Such a configuration encourages the distaltip 140 to follow a path of least resistance through the tissue asopposed to digging into the surfaces of the sacrum and the ilium.

The edges of the distal tip 140 in the tapered region may be curved tofacilitate the distal tip passing into tissue as opposed to the distaltip 140 cutting through the tissue. Similarly, the distal end may becurved or otherwise shaped with an unsharpened end.

Forming the first cutting assembly 132 with this configurationfacilitate extending the first cutting assembly 132 through the tissuewhile minimizing the potential that the first cutting assembly 132 cutstoo deeply into the bone on the sacrum or the ilium. Cutting into thebone too deeply could weaken the bone and potentially inhibit theability of the undercutting system to prepare the surfaces of both thesacrum and the ilium.

The first cutting assembly 132 may include a plurality of links that arepivotally mounted to each other. The plurality of links 150 provides thefirst cutting assembly 132 with rigidity along a radial-tangentialdirection while providing the first cutting assembly 132 withflexibility in a distal-proximal direction. This configuration allowsthe first cutting assembly 132 to be deflected to a substantiallyperpendicular orientation after the undercutting guide is inserted whileallowing the undercutting system to be rotated to prepare the region forthe sacroiliac joint fusion.

The corners of the plurality of links 150 may be sharpened to providecutting as the undercutting system is rotated. Such cutting caused bythe plurality of links 150 will not negatively affect the operation ofthe undercutting system because the distal tip 140 will have formed apath through the tissue prior to the plurality of links reaching thetissue.

During the process of probing the sacroiliac joint with the firstcutting assembly 132, the first cutting assembly 132 may be partiallyextended from the undercutting guide and then rotate the undercuttingguide to form a generally circular path between the sacrum and theilium. Once the user determines the path is generally clear such as by areduced resistance to rotation of the undercutting guide, the firstcutting assembly 132 may be further extended from the undercutting guideso that a region having a larger radius may be prepared. This processmay be repeated until a region having a desired radius is prepared.

The first cutting assembly 132 is then withdrawn from the undercuttingguide and the second cutting assembly is inserted into the undercuttingguide. When withdrawing the first cutting assembly 132, it is notnecessary for the first cutting assembly 132 to be slowly withdrawn byreversing the procedure by which the first cutting assembly 132 isgradually extended into the region between the sacrum and the ilium.

Rather, the undercutting guide may include a mechanism that allows thefirst cutting assembly to be rapidly withdrawn from the undercuttingguide. One such mechanism for quickly removing the first cuttingassembly 132 is to provide a button on at least one of the undercuttingguide or the first cutting assembly 132 that is movable between anengaged position and a disengaged position. This button mechanism mayoperate similar to a conventional caulking gun.

When the button is in the engaged position, the first cutting assembly132 may be advanced slowly such as by rotating a portion of theundercutting guide. When the button is in the disengaged position, thefirst cutting assembly 132 may slide with respect to the undercuttingguide to facilitate quickly removing the first cutting assembly 132 fromthe undercutting guide 132.

The second cutting assembly 232 is illustrated in FIGS. 10-13 and isused to cut a large portion of the tissue between the sacrum and theilium to prepare for fusion of the sacroiliac joint. In this regard, thesecond cutting assembly 232 may include a cutting tip 240 having anelongated configuration with an aperture 242 extending through a centralportion thereof. The first and second side surfaces 244 of the cuttingtip 240 may have sharpened edges to facilitate the second cuttingassembly 232 being used to simultaneously cut tissue from the sacrum andillium sides of the second cutting assembly 232.

An end surface 246 of the cutting tip 240 that extends between the firstand second side surfaces 244 may be curved. The end surface 246 of thecutting tip 240 may also include a sharpened edge, which facilitatescutting tissue that is proximate the end. Similar to the first cuttingassembly 132, a distal end 246 of the second cutting assembly 232 maynot have a sharpened surface to minimize the potential of the secondcutting assembly 232 cutting too deeply into the surfaces of the sacrumand the ilium.

Opposite ends of the cutting tip 240 may have sharpened surfaces tofacilitate performing cutting when the undercutting guide is rotated inclockwise and counterclockwise directions.

Similar to the first cutting assembly 132, the second cutting assembly232 may include a plurality of links 250 that are pivotally mounted toeach other. The plurality of links 250 provides the second cuttingassembly 232 with rigidity along a radial-tangential direction whileproviding the second cutting assembly 232 with flexibility in adistal-proximal direction. This configuration allows the second cuttingassembly 232 to be deflected to a substantially perpendicularorientation after the undercutting guide is inserted while allowing theundercutting system to be rotated to prepare the region for thesacroiliac joint fusion.

During the process of cutting the tissue in the sacroiliac joint withthe second cutting assembly 232, the second cutting assembly 232 may bepartially extended from the undercutting guide and then rotate theundercutting guide to cut tissue and form a generally circular pathbetween the sacrum and the ilium. Once the user determines the path isgenerally clear such as by a reduced resistance to rotation of theundercutting guide, the second cutting assembly 232 may be furtherextended from the undercutting guide so that tissue can be cut from aprogressively larger radius. This process may be repeated until a regionhaving a desired radius is prepared.

The second cutting assembly 232 is then withdrawn from the undercuttingguide and the third cutting assembly 332 is inserted into theundercutting guide. The third cutting assembly 332 is illustrated inFIGS. 14-17 and is used to further prepare the surfaces of the sacrumand the ilium for fusion of the sacroiliac joint.

The distal tip 340 on the third cutting assembly 332 may have a widththat is greater than a width of the distal tip 240 used in conjunctionwith the second cutting assembly 232. The third cutting assembly 332thereby facilitates further preparing the surfaces of the sacrum and theilium by cutting and/or scraping tissue from the sacrum and the ilium.

The distal tip 340 may have a generally diamond shape that enables atleast a portion of the distal tip 340 to conform to the surface of thesacrum or the ilium when the distal tip is deflected from an orientationthat is substantially aligned with the portions that are adjacentthereto.

An edge surface 342 of the distal tip 340 that extends substantiallytherearound may be sharpened to facilitate performing a cutting actionalong both the sacrum and the ilium sides of the distal tip.Additionally, the edge surfaces 342 on opposite sides of the distal tip340 may be sharpened to facilitate performing a cutting action when thethird cutting assembly 332 is rotated in clockwise and counterclockwisedirections.

During the process of preparing region between the sacrum and the iliumfor the sacroiliac joint fusion, the distal tip of the cutting assemblymay extend slowly from the undercutting guide. The undercutting systemmay include a visual indicator on a region thereof that remains outsidethe patient during the use thereof. In certain embodiments, at least oneof the undercutting guide and the cutting assembly may include a visualindicator that includes a visual representation of how far the distaltip is extending therefrom. Alternatively or additionally, theundercutting system may include a numeric value of the distance to whichthe distal tip is extending therefrom.

The undercutting system 430 generally includes a cutting assembly 432and an undercutting guide 434, as illustrated in FIG. 18. The cuttingassembly 432 may have an elongated configuration with a proximal end 440and a distal end 442. The proximal end 440 may be located outside of thepatient while the undercutting system 430 is in use.

At least a portion of the cutting assembly 432 may be formed withflexibility along a first plane and rigidity along a second plane thatis oriented generally perpendicular to the first plane.

In certain embodiments, the portion of the cutting assembly 432 that isproximate to the cutting head 438 is formed from a resilient material.Forming at least a portion of the cutting assembly 432 from theresilient material enables the cutting head 438 to exert pressureagainst the surface of the ilium 414 and/or the sacrum 416 to removetissue from the surfaces thereof to prepare the surfaces for fusion.This configuration also enables the cutting head 438 to be deflected inresponse to a shape of the region 412 between the ilium 414 and/or thesacrum 416 that is not flat and/or not transverse to the aperture eventhough FIG. 1 illustrates that the aperture 410 is oriented generallyperpendicular to the surfaces of the ilium 414 and the sacrum 416.

A cutting head 438 may be attached to the distal end 442 of the cuttingassembly 432. The cutting head 438 may take a variety of configurations,as is discussed below in more detail.

The undercutting guide 434 may have a generally cylindrical shape with aproximal end 444 and a distal end 446. The proximal end 444 may belocated outside of the patient while the undercutting system 430 is inuse.

The undercutting guide 434 may have a guide channel 450 that extendstherethrough to facilitate guiding the cutting head 438 to a desiredlocation in the region 412 between the ilium 414 and the sacrum 416. Theguide channel 450 may have a size that is slightly larger than a size ofthe cutting assembly 432 to enable the cutting assembly 432 to freelymove with respect to the guide channel 450. The guide channel 450 may beformed with a profile that conforms to a profile of the cutting assembly432. For example, the guide channel 450 and the cutting assembly 432 maybe formed with a circular profile.

A proximal portion 452 of the guide channel 450 proximate the proximalend 444 may be generally aligned along an axis of the undercutting guide434. A distal portion 454 of the guide channel 450 proximate the distalend 446 may be oriented generally transverse to the axis of theundercutting guide 434. An intermediate portion 456 of the guide channel450 may be curved to provide a transition between the proximal portion452 and the distal portion 454.

To facilitate directing the cutting assembly 432 and the guide 434 intothe aperture 410, the guide shaft 436 may be used. The guide shaft 436may extend from the ilium 414 to a location outside of the patient'sbody. It is also possible to form the guide shaft 436 in shorterlengths.

The guide shaft 436 may have an inner surface that generally conforms toan outer surface of the undercutting guide 434. In certain embodiments,the guide shaft 436 and the undercutting guide 434 both have a generallycircular profile. The undercutting guide 434 may have a diameter that isslightly smaller than a diameter of the guide shaft 436 so that theundercutting guide 434 may freely move with respect to the guide shaft436.

The cutting assembly 432 is initially positioned so that an end of thecutting head 438 is positioned within the guide channel 450, asillustrated in FIG. 19. The undercutting guide 434 is moved into theshaft 436 so that the distal end 458 of the undercutting guide 434 ispositioned proximate the sacrum 416, as illustrated in FIG. 20.Depending on the shape of the distal end 458, it may be necessary toremove a portion of the sacrum 416 that is adjacent to the distal end458 so that the distal end 458 is partially recessed in the sacrum 416.

The cutting assembly 432 is then moved inwardly so that the cutting head438 extends beyond the guide channel 450 and contacts the surfaces ofthe ilium 414 and/or the sacrum 416. The undercutting system 430 isrotated to cause the cutting head 438 to remove cartilage from thesurface of the ilium 414 and/or the sacrum 416 to thereby prepare theilium 414 and the sacrum 416 for fusion.

A variety of techniques may be used to rotate the undercutting system430. In certain embodiments, the undercutting system 430 is rotated byhand. In other embodiments, a powered device or an energy storage devicemay be used to cause the undercutting system 430 to rotate. An exampleof a powered device that may be used to rotate the undercutting system430 is a drill.

A person of skill in the art will appreciate that this process causes acircular or partially circular region to be prepared. Depending on thearea of the bone surface that must be prepared, the cutting assembly 432may be moved with respect to the guide 434 to cause a size of theprepared region to be increased. FIG. 21 illustrates with dotted lineswhere the cutting head 438 has been extended several different distancesfrom the guide 434 to prepare a successively larger area of the ilium414 and/or the sacrum 416.

Depending on a width of the cutting head 438, it may be necessary tomove the undercutting guide 434 with respect to the ilium 414 to causethe cutting head 438 to be alternately positioned proximate the surfacesof the ilium 414 and the sacrum 416.

The cutting assembly 432 may be fabricated from a plurality of layers460 of resilient material, as illustrated in FIG. 22. In certainembodiments, the layers 460 can be formed from nitinol. To enhance theability of the layers to slide with respect to each other and tetherbroken pieces, a low friction high tensile strength material such asmylar may be placed between each of the layers 460 of resilientmaterial.

Forming the cutting assembly 432 with this configuration enables thecutting assembly 432 to bend as the cutting assembly 432 moves throughthe intermediate portion 456. This configuration also provides thecutting assembly 432 with lateral strength to cut through the cartilagebetween the ilium 414 and the sacrum 416.

At least a portion of the cutting assembly 432 may be hollow to enablefluid to be transported into and out of the region 412. The cuttingassembly 432 may include more than one fluid transmission channel suchthat one of the fluid transmission channels may be used for delivering arinsing fluid and another fluid transmission channel may be used toremove the rinsing fluid and debris.

At least a portion of the outer surface of the cutting assembly 432 maybe covered with a plurality of bristles. The bristles may be used tocatch debris generated by the cutting head 438. The cutting assembly 432may be periodically withdrawn from the guide 434 so that the debris canbe removed from the bristles.

In one configuration, the cutting head 438 has a generally cylindricalcutting section 462 and a cutting tip 464, as illustrated in FIG. 22.The cylindrical cutting section 462 may be oriented generally transverseto an axis of the cutting assembly 432. The cylindrical cutting section462 may have a cutting surface 466 proximate opposite ends thereof.

Forming the cylindrical cutting section 462 with the precedingconfiguration enables the cutting to be performed at both ends 470, 472of the cutting assembly 432 when the cutting assembly 432 is rotatedclockwise or counter clockwise. Additionally, this configuration enablescutting to be performed on both sides 474, 476 of the cutting head 438.

The cutting tip 464 extends from a distal side of the cylindricalcutting section 462. The cutting tip 464 may be a pointed configuration.The cutting tip 464 may have cutting surfaces 468 proximate both ends480, 482 thereof as well as along a tip 484. The cutting tip 464 therebyenables the cartilage to be cut as the cutting assembly 432 is insertedfurther.

The cutting head 438 may have a variety of configurations using theconcepts of the invention. FIG. 23 illustrates an alternativeconfiguration of the cutting head 438 in which the cutting tip 464 isshorter than the cutting tip 464 illustrated in FIG. 22. The cuttinghead 438 in FIG. 24 is generally in the shape of a flat-ended loopcurette. The cutting head 438 in FIG. 25 is generally in the shape of aring curette. A person of skill in the art will appreciate that avariety of surfaces of the preceding cutting head configurations may becutting surfaces.

In another embodiment, at least a portion of the cutting assembly 532may be formed from a plurality of links 534, as illustrated in FIG. 26.The links 534 may be attached to an operator shaft 536. The links 534may be pivotally attached to each other. This configuration enables thecutting assembly 532 to bend such as when passing through theintermediate portion 556. The links 534 also provide the cuttingassembly 532 with lateral strength so that cutting can occur when thecutting assembly 532 is rotated.

A cutting head 538 may be operably attached to a distal link 534. Themounting of the cutting head 538 to the distal link 5 may enable thecutting head 538 to be detached from the distal link 534 such as when itis desired to use another type of cutting head 538 or when the cuttinghead 538 becomes dull and needs to be replaced. The cutting head 538 mayhave a similar configuration to the cutting heads 38 illustrated inFIGS. 22-25.

The links 534 may have a variety of configurations using the concepts ofthe invention. One configuration of the links 534 a is illustrated inFIGS. 27-29. The links 534 a in this configuration are shaped similar toa conventional bicycle chain and include alternating big and smalllinks. Opposite ends of the big links and the small links are pivotallyattached to each other.

An alternative configuration of the links 534 b is illustrated in FIGS.30-32. Each of the links 534 b is formed substantially similar to eachother. The links 534 b each may have a generally oval shape with a firstend 540 and a second end 542. The first end 540 may have a tab extendingtherefrom. The second end 542 may include a recess that is adapted toreceive the tab for pivotal mounting of two adjacent links 534.

Another configuration for the links 534 c is illustrated in FIGS. 33-35.The links 534 c may be formed by cutting a piece of metallic or plasticmaterial. The cuts enable the cutting assembly to be curved. The cutsmay be formed to produce a plurality of blocks that each have a pointedsurface at one end thereof, as illustrated in FIG. 36. Alternatively oradditionally, the cuts may be formed to provide a series of blocks thatare each connected with a narrow diameter section.

Yet another configuration of the cutting assembly 532 includes forming aplurality of cuts 544 in a tube, as illustrated in FIG. 36. The cut tubethereby permits bending along at least one axis. A person of skill inthe art will appreciate that a variety of techniques may be used forform the cuts.

Still another embodiment of the cutting assembly 532 is illustrated inFIG. 37. This embodiment includes a plurality of bristles or burrs 546on a surface of the links. As is discussed above, the bristles or burrs546 may be used to collect debris that is generated in the cuttingprocess.

Another configuration of the cutting assembly 632 is illustrated in FIG.38. The cutting assembly 632 includes an operator shaft 634 and at leastone cutting head 638 operably connected to a distal end of the operatorshaft 634.

In many configurations, the operator shaft 634 may be relatively rigid.In other configurations, the shaft may be flexible similar to theconfiguration of a speedometer cable that is used on an automobile orbicycle.

Similar to the undercutting guide 34 illustrated in FIGS. 2-4, theoperator shaft 634 may have a shape that conforms to a shape of theguide shaft 636. In certain embodiments, the operator shaft 634 and theguide shaft 636 both have a substantially cylindrical shape. A diameterof the operator shaft 634 is slightly smaller than a diameter of theguide shaft 636. The configuration enables the cutting assembly 632 toslide with respect to the guide shaft 336.

A central portion of the operator shaft 634 may be hollow to facilitateintroducing a flushing fluid and/or removing debris that has beengenerated from the use of the cutting assembly 632.

While the figures illustrate that the cutting assembly 632 includes twocutting heads 638, the number of cutting heads may be varied. Forexample, a single cutting head 638 or a larger number of cutting headsmay be used.

The cutting head 638 may be positioned in a retracted position (FIG. 39)and an extended position (FIG. 40). When in the retracted position, anouter surface of the cutting head 638 is generally no wider than a widthof the operator shaft 634. Using such a configuration enables thecutting assembly 632 to be moved through the guide shaft 636 without thecutting head 638 impeding such movement.

When in the extended position, the cutting head 638 extends outwardlyfrom the operator shaft 634. A cutting surface on the cutting head 638engages tissue between the ilium 614 and the sacrum 616 and therebycauses the tissue to be cut so that the tissue may be removed.

In certain embodiments, centrifugal force caused by rotation of thecutting assembly 632 causes the cutting head 638 to move from theretracted position to the extended position. Rotating the cuttingassembly in an opposite direction causes the cutting head 638 to moveback to the retracted position. It is also possible to use mechanicalmechanisms for moving the cutting head 638 between the retracted andextended configurations.

The cutting head 638 may have a variety of configurations using theconcepts of the invention. In certain embodiments, the cutting head 638has a curved configuration so that an outer surface 640 of the cuttinghead 638 at least partially conforms to an outer surface of the operatorshaft 634.

In one embodiment, the cutting head 638 includes a plurality of cuttingelements 642 on the outer surface 640, as illustrated in FIG. 41. Whilenot illustrated, the cutting elements 642 may also be provided on theupper and lower surfaces 644, 646 of the cutting head 638. As thecutting elements 642 engage tissue, the cutting elements 642 cause bitsof the tissue to be cut off similar to the action of a cheese grater.

An alternative configuration of the cutting head 638 includes aplurality of burrs or bristles 650 on the outer surface 640, the uppersurface 644 and the lower surface 646, as illustrated in FIG. 42. Theburrs or bristles 650 may also be provided on the upper and lowersurfaces of the cutting head 638. As the burrs or bristles 650 engagetissue, the burrs or bristles 650 cause bits of the tissue to be cutoff. The bits of tissue may be retained in the burrs or bristles 650 tofacilitate removing the bits of tissue.

Another configuration of the cutting head 638 includes a loop curette652 formed therein, as illustrated in FIG. 43. The loop curette 652 maybe positioned proximate a distal end of the cutting head 638. While theloop curette 652 is illustrated as occupying a relatively small portionof the cutting head 638, it is possible for the loop curette 652 tooccupy a larger portion of the cutting head 638.

Still another configuration of the cutting head 638 includes cuttingedges 654 proximate upper and lower surfaces 644, 646 thereof, asillustrated in FIG. 44. Intermediate the cutting edges 654 may be arecessed region 652.

Another configuration of the cutting assembly 732 includes areciprocating cutting head 736, as illustrated in FIG. 45. Alternativelyor additionally, the cutting head 738 may be rotated to produce thecutting action.

The cutting assembly 732 includes an operator shaft 734 and a cuttinghead 738 that is operably attached to a distal end of the operator shaft734. Depending on the anticipated operating mechanism of the cuttingassembly 732, the operator shaft 734 may be reciprocally or rotationallymounted in the guide shaft 736.

The cutting head 738 may have a plurality of cutting teeth formedtherein. Alternatively, the cutting head 738 may have an abrasiveattached to a surface thereof having a configuration that is similar toa rasp. The cutting head 738 may be fabricated from a flexible materialthat enables the cutting head 738 to be curved from an orientationparallel to an axis of the cutting assembly 732 to an orientationperpendicular the axis of the cutting assembly 732, as illustrated inFIG. 45.

The guide shaft 736 may include a plurality of guide rollers 740 thatfacilitate changing the orientation of the cutting head 738 fromparallel to the axis of the cutting assembly 732 to the orientationperpendicular the axis of the cutting assembly 732. Alternatively, atube or a sheet of durable material may be used to guide the cuttinghead 738.

The guide shaft 736 may include at least one tube or channel 744 tofacilitate delivering an irrigation fluid or suction that are used toremove debris generated by the cutting process.

Another configuration of the cutting assembly 832 includes anumbrella-type mechanism, as illustrated in FIGS. 46-47. The cutting head838 may include at least two cutting arms 840. The cutting arms 840 areinitially in a retracted configuration (FIG. 46). After insertion of thecutting assembly 832, the cutting arms 840 are moved to the extendedconfiguration (FIG. 47).

Similar to the cutting heads discussed with respect to the otherconfigurations of the cutting assembly, the cutting arms 840 have asharp surface on an outer surface thereof. The sharp surface may be onthe upper edge, the lower edge and/or the outer edge. A variety oftechniques may be used to provide the sharp surface.

The cutting arms 840 are initially in the retracted position. When inthe retracted position, the outer surface of the cutting arms 840 iswithin a diameter of the guide tube 836. After the cutting assembly 832is inserted into the aperture 10, the cutting arms 840 are allowed tomove from the retracted position to the extended position.

The cutting arms 840 may be biased to the extended position. Once thecutting arms 840 are in the extended position, the operator shaft 834may be rotated to cause the tissue to be removed from between the ilium814 and the sacrum 816. Similar to the other configurations, the cuttingassembly 832 may include a channel for delivering irrigation fluid orvacuum.

The cutting arms 840 may be pivotally mounted to the operator shaft 834so that the cutting arms 840 may pivot with respect to the operatorshaft 834 when in the extended position, as illustrated in FIGS. 48 and49. Pivoting of the cutting arms 840 enables the cutting arms to conformto a surface of the ilium or the sacrum when the surface is notsubstantially perpendicular to the axis of the operator shaft 834.

In another configuration of the cutting assembly 932, the cutting head938 includes a plurality of cutting arms 940 extending therefrom, asillustrated in FIG. 50. The cutting arms 940 may have a generallyrectangular configuration with a cutting surface 942 along oppositeedges thereof. A cutting surface 944 may also be provided on a distaledge of the cutting arms 940. The configuration of the cutting arms 940provides the cutting arms 940 with rigidity so that the cutting arms 940resist bending sideways in response to rotation of the cutting assembly932 during the cutting process.

The cutting arms 940 may be formed from a flexible material so that thecutting arms may be moved between a refracted configuration (FIG. 50)and an extended configuration (FIG. 51). When the cutting arms 940 arein the retracted configuration, the cutting arms 940 are substantiallywithin a diameter of the cutting assembly 932.

The cutting assembly 932 has a deflector mechanism 946 mounted at adistal end thereof. The deflector mechanism 942 includes a curved orangled surface that changes from an orientation generally aligned withan axis of the cutting assembly 932 to an orientation generallyperpendicular to the axis of the cutting assembly 932.

A distal end of the cutting arms 940 contacts the deflector mechanism942, as cutting head 938 is moved towards the deflector mechanism 942.The deflector mechanism 942 urges the cutting arms 940 to be deflectedto the extended configuration, as illustrated in FIG. 51. When thecutting arms 940 are in the extended configuration, the cutting arms 940may engage the tissue between the ilium 914 and the sacrum 916 to causeit to be removed therefrom to prepare for the sacroiliac fusion.

Once the cutting arms 940 are in the extended configuration, the cuttingassembly 932 may be rotated to cause the cutting surfaces 942, 944 toengage the tissue between the ilium 914 and the sacrum 916. In certainsituations, it may be necessary to move the cutting assembly 932 so thatthe cutting surfaces 942, 944 alternatively engage the surface of theilium 914 and the sacrum 916.

Once the cutting process is completed, the cutting assembly 932 is movedtowards a proximal end. This movement causes the cutting arms 940 tomove from the extended configuration to the retracted configuration sothat the cutting assembly 932 may be withdrawn.

An alternative configuration of the cutting assembly 932 has cuttingarms 940 that are tapered, as illustrated in FIG. 52. In thisconfiguration, the cutting arms 940 have a greater width proximate aproximal end thereof than proximate a distal end thereof. Cuttingsurfaces 946 may be provided on the sides of the cutting arms 940.

In another configuration, a distal end of the cutting assembly 1032 hasa generally cylindrical configuration, as illustrated in FIG. 53. Thecutting assembly 1032 has a plurality of slits 1038 formed therein todefine the cutting arms 1040. The slits 1038 do not extend all the wayto the distal end of the cutting assembly 1032 but rather end a distancefrom the distal end of the cutting assembly 1032 to define an endportion 1042.

The surfaces of the cutting assembly 1032 are cutting surfaces. Avariety of techniques may be used for fabricating the cutting surfaces.Examples of the cutting surfaces include sharpened, a roughened textureor burrs attached to a surface thereof.

The cutting assembly 1032 is initially in a retracted position. When thecutting assembly 1032 is in the retracted position, an outer surface ofthe cutting assembly 1032 may be substantially straight, as illustratedin FIG. 53.

As the cutting assembly 1032 is inserted into the aperture 1010, the endportion 1042 engages the sacrum 1016. In certain embodiments, a recess1044 may be formed in the sacrum 1016 that is configured to receive atleast partially receive the end portion 1042.

When the cutting assembly 1032 continues to move towards the sacrum1016, the cutting arms 1040 are deflected outwardly, as illustrated inFIG. 54, until the cutting arms 1040 are in the extended configuration.When the cutting arms 1040 are in the extended configuration, thecutting assembly 1032 may be rotated to cause tissue between the ilium1014 and the sacrum 1016 to be removed.

The length of the slits 1038 determines how far the cutting arms 1040outwardly extend when in the extended position. In certain embodiments,it may be necessary to use several different cutting assemblies withprogressively longer slits 1038 to enable a progressively larger surfacearea between the ilium 1014 and the sacrum 1016 to be prepared.

Alternatively or additionally, a central shaft 10746 may be provided inthe cutting assembly 1032. The central shaft 1046 may be operablyconnected to the end portion 1042. Holding the central shaft 1046 as theother portions of the cutting assembly 1032 are moved toward the distalend thereof may be used to urge the cutting arms 1040 from the retractedposition to the extended configuration. Such a process enables thecutting arms 1040 to be moved to the extended position without placingany forces on the sacrum 1016.

In another configuration of the cutting assembly 1132, the cuttingassembly 1132 may include a central shaft 1138 and a cutting head 1140that extends from a distal end thereof, as illustrated in FIG. 55. Inthis configuration, a size of the cutting assembly 1132 is greaterproximate where the cutting head 1140 extends therefrom.

The cutting head 1140 may have sharp surfaces on upper and lowersurfaces 1142, 1144 thereof to facilitate removing tissue from surfaceof the ilium 1114 and the sacrum 1116. The cutting head 1140 may alsohave a sharp surface on an end 1146 thereof.

A height of the cutting head 1140 may be less than a distance betweenthe ilium 1114 and the sacrum 1116. In such a configuration, the centralshaft 1138 may be moved inward or outward so that the cutting surfacesalternatively engage the ilium and the sacrum.

The aperture 1110 formed in the ilium 1114 may have a shape thatgenerally conforms to a shape of the cutting assembly 1132, asillustrated in FIG. 56. In certain embodiments, the aperture 1110 may beformed in two parts.

The first aperture part 1150 may have a generally circularconfiguration, such as may be formed by a conventional drill. The secondaperture part 1152 may be generally rectangular with sides that aresubstantially parallel to each other. The second aperture part 1152 maybe formed using a variety of techniques. An example of one such suitabletechnique is a reciprocating saw.

It is also possible to form the second aperture part 1152 having otherconfigurations. The only important criterion is that the second aperturepart has a length and a width that are larger than a length and a widthof the cutting head 1140. An example of one other suitable technique isforming the second aperture part 1152 using a drill.

The drill bit used to form the second aperture part 1152 may have asmaller size than the drill bit used to form the first aperture part1150. The drill bit used to form the second aperture part 1152 may belaterally offset from the position of the drill bit used to form thefirst aperture part 1150 so that the first aperture part 1150 and thesecond aperture part 1152 intersect.

Another configuration of the cutting assembly 1232 uses a laser beam1240 for removing tissue from between the ilium 1214 and the sacrum1216, as illustrated in FIG. 57. The cutting assembly 1232 may berotational to facilitate removing tissue in all directions around theaperture 1210.

The cutting assembly 1232 may include a reflective device 1242 to directthe laser beam 1240 between from an orientation generally aligned withan axis of the cutting assembly 1232 to an orientation generallyperpendicular to the axis of the cutting assembly 1232. A person ofskill in the art will appreciate that the reflective device 1242 maytake a variety of configurations depending on the type of laser beam1240 used with the cutting assembly 1232.

It may be necessary to move the cutting assembly 1232 inward and outwardto enable tissue to be removed from between the surfaces of the ilium1214 and the sacrum 1216. Alternatively or additionally, the reflectivedevice 1242 may be movably mounted in the cutting assembly 1232 tocontrol the direction of the laser beam.

An example of one suitable laser that may be used in conjunction withthis embodiment of the cutting assembly 1232 is an excimer laser. Aperson of skill in the art will appreciate that other apparatuses thatemit an energy beam that is capable of removing the tissue between theilium 1214 and the sacrum 1216 in a controlled manner may also be used.

Another embodiment of the invention relates to the use of chemicals,examples of which include acids and enzymes to dissolve and/or removetissue from between the ilium and the sacrum to thereby prepare forfusion of the sacroiliac joint may also be used. A variety of techniquesmay be used for supplying the chemicals and thereafter removing thechemicals and the dissolved tissue.

A fluid jet technology may be used to remove the tissue from between theilium and the sacrum to prepare for fusion of the sacroiliac joint.Examples of the fluid jet technology that may be used includehydrocision.

A particle stream may be used to prepare the surfaces of the ilium andthe sacrum for fusion of the sacroiliac joint may be used. One suchstream of particle is a sand blaster. The particles may have a surfacethat is rough or abrasive so facilitate abrading or otherwise removingthe tissue from between the ilium and the sacrum.

The particles used should be biocompatible or bioresorbable to minimizethe potential of side effects on the patient if the particles are notall removed from the patient once the surfaces of the ilium and thesacrum are prepared.

The particle stream may be used in conjunction with at least two holesthat are formed in the ilium and/or the sacrum. One of the holes may beused for introducing the particles into the region between the ilium andthe sacrum. A separate hole may be used for collecting the particles andthe tissue removed.

As an alternative or in addition to the sharp surfaces describe in thevarious embodiments discussed herein, the surfaces could be rough and/orabrasive to facilitate removing the tissue between the ilium and thesacrum using abrasion, as opposed to cutting.

The abrasive action may be provided by particles attached to the surfaceof the cutting assembly. Alternatively or additionally, the abrasiveaction may be provided by wires or other materials that extend from thesurface of the cutting assembly.

Another embodiment of the cutting assembly 1332 is directed toarticulating rongeurs 1340 that may be used in conjunction with adocking cannular 1342, as illustrated in FIG. 58. The articulatingrongeurs 1340 may generally include a cutting mechanism 1350, a controlmechanism 1352 and an elongated section 1354 that interconnects thecutting mechanism 1350 and the control mechanism 1352.

The cutting mechanism 1350 may operate in a variety of manners. In oneconfiguration, the cutting mechanism 1350 includes two jaws 1358 thatare pivotally mounted to each other for movement between an openconfiguration and a closed configuration.

At least one of the jaws 1358 may have a cutting surface 1360. As thejaws 1358 are moved to the closed configuration, the cutting surface1360 engages the tissue and thereby cuts away the tissue. The process isrepeated until a desired amount of tissue is removed from between theilium 1314 and the sacrum 1316.

At least one of the jaws 1358 may include a tapered end to facilitatemoving the jaw 1358 between the tissue and the ilium or the sacrum tothereby enhance the ability to prepare the surfaces of the ilium and thesacrum for the sacroiliac fusion.

A length of the cutting mechanism 1350 may be less than an innerdiameter of the docking cannula 1342 to facilitate passing the cuttingmechanism 1350 through the docking cannula 1342.

The control mechanism 1352 facilitates operation of the cuttingmechanism 1350 from a position outside of the space between the ilium1314 and the sacrum 1316. In certain embodiments, the control mechanism1352 may be designed for positioning outside of the patient's body whenused.

The control mechanism 1352 is operably connected to the cuttingmechanism 1350. In certain embodiments, there is a mechanical connectionbetween the control mechanism 1352 and the cutting mechanism 1350. Forexample, the control mechanism 1352 may include two handles 1362 thatare pivotally mounted to each other. Pivoting of the handles 1362towards each other causes the jaws to pivot to each other. The handles1362 may be biased apart from each other so that the jaws are initiallyin the open configuration.

Alternatively, there may be an electrical connection between the controlmechanism 1352 and the cutting mechanism 1350. In such a configuration,the control mechanism 1352 may include a switch or other mechanism forcausing the cutting mechanism 1350 to be activated. A mechanism may beprovided on the cutting mechanism 1350 to receive the signal from thecontrol mechanism 1352 and thereby activate the cutting mechanism 1350.

A person of skill in the art will appreciate that other mechanisms maybe used for operably connecting the control mechanism 1352 and thecutting mechanism 1350. Examples of such suitable alternative mechanismsinclude pneumatic, vacuum and hydraulic.

The elongated section 1354 operable connects the cutting mechanism 1350and the control mechanism 1354. The elongated section 1354 may be formedwith a length that provides a desired distance between the cuttingmechanism 1350 and the control mechanism 1354. In certain embodiments,the elongated section 1354 has a length of between about 2 inches and 18inches.

While the elongated section 1354 is illustrated as being substantiallystraight, it is possible for the elongated section 1354 to have avariety of other configurations that enable the cutting mechanism 1350to be operated between the ilium 1214 and the sacrum 1316 while enablingthe control mechanism 1352 to be operated from a convenient positionoutside of the patient. The elongated section 1354 may be rigid orflexible using the concepts of the invention.

Yet another configuration of the cutting assembly 1432 involves formingthe cutting assembly 1432 as an endius-type shaver, which is used inconjunction with a cannula, as illustrated in FIG. 59.

The endius-type shaver includes a cutting head 1438 attached to a distalend thereof. The cutting head 1438 may include a plurality of teethand/or an abrasive. Rotation of a shaft within the cutting assembly 1432causes the cutting head 1438 to engage the tissue between the ilium 1414and the sacrum 1416 and thereby cut the tissue to prepare for fusion ofthe sacroiliac joint.

Another configuration used for preparing the surfaces of the ilium 1514and the sacrum 1516 for fusion includes passing a line 1540 having anabrasive surface through two apertures 1542, 1544 in the ilium 1514, asillustrated in FIG. 60. As the line 1540 is moved in an oscillatingmotion, the abrasive causes tissue to be removed from the surfaces ofthe ilium 1514 and the sacrum 1516 to thereby prepare the surfaces forthe fusion of the sacroiliac joint. Periodically, the separated tissuemay be removed from between the ilium 1514 and the sacrum 1516. A personof skill in the art will appreciate that a variety of techniques may beused.

While FIG. 60 illustrates that two apertures 1542, 1544 are used inconjunction with the process, it is possible to use additional aperturesto prepare a larger surface area for the fusion of the sacroiliac joint.

Another configuration that may be used to prepare the sacroiliac jointfor fusion involves forming at least one aperture 1640 in the ilium 1614using a device such as a hole saw that enables a substantially solidpiece 1642 to be remove from the ilium 1614, as illustrated in FIG. 61.

Once the piece 1642 is removed, tissue is removed from the inner surfaceof the removed piece 1642 to prepare the inner surface of the removedpiece 1642 for fusion. A surface of the sacrum 1616 below the removedpiece is also prepared by removing tissue from the surface thereof toprepare the inner surface of the sacrum 1616 for fusion.

Thereafter, the removed piece 1642 is replaced. A variety of techniquesmay be used to maintain the piece 1642 in a stationary position withrespect to the ilium 1614 so that bone may grow between the preparedsurfaces to cause fusion of the sacroiliac joint.

Each of the apertures 1640 may have a size of up to about 1 inch. Incertain embodiments, the apertures 1640 each have a diameter of betweenabout ½ and ¾ of an inch. The number of apertures 1640 formed in theilium may be selected to provide adequate prepared surface area on theilium 1614 and the sacrum 1616 for fusion. There may be up to about 10apertures 1640. In certain embodiments, there are between two and threeapertures 1640.

While this configuration for preparing the surfaces of the ilium 1614and the sacrum 1616 for the fusion of the sacroiliac joint is moreinvasive than many of the other techniques described herein, it isconsiderably less invasive than the prior art techniques for fusion ofthe sacroiliac joint.

Another configuration of the cutting assembly 1732 is illustrated inFIG. 62. The cutting assembly 1732 may be used in conjunction with acannula that is positioned in the aperture formed in the ilium. Thecutting assembly 1732 includes an undercutting guide 1734 and a cuttinghead 1738.

The cutting head 1738 includes an elongated shaft 1742 and a cuttingextension 1744. The cutting extension 1744 extends from one side of theelongated shaft 1742. Upper and lower surfaces 1750, 1752 of the cuttingextension 1744 may have a sharpened or abrasive surface to facilitateremoving material from between the ilium and the sacrum. An end surface1754 of the cutting head 1738 may also have a sharpened or abrasivesurface.

The cutting extension 1744 is mounted in an offset configuration in theundercutting guide 1734, as illustrated in FIG. 62. Mounting the cuttingextension 1744 in such a manner enables the cutting extension 1744 to bemoved between a refracted configuration (FIG. 62) and an extendedconfiguration (FIG. 63).

When the cutting extension 1744 is in the refracted configuration, thecutting extension 1744 is substantially within a diameter of theundercutting guide 1734 to facilitate inserting and removing the cuttingassembly 1732. When the cutting extension 1744 is in the extendedconfiguration, the cutting extension 1744 extends beyond theundercutting guide 1734 so that the cutting extension 1744 may be usedto remove tissue from between the ilium and the sacrum.

The cutting extension 1744 may be maintained in a stationary positionwith respect to the undercutting guide 1734 and then the cuttingassembly 1732 may be rotated, as illustrated by the dashed lines in FIG.63. Depending on the thickness of the cutting extension 1744, it may benecessary to move the cutting assembly 1732 inward or outward to clearthe surfaces of the ilium and the sacrum.

Multiple cutting head 1738 having cutting extensions 1744 of differentlengths may be used in conjunction with the cutting assembly 1732 tothereby enable progressively larger surface areas on the ilium and thesacrum to be prepared for the sacroiliac fusion.

Alternatively or additionally, the cutting extension 1744 may be formedwith a telescoping configuration, as illustrated in FIGS. 60 and 61. Thecutting extension 1744 may be in an initial position where the cuttingextension 1744 is substantially within a diameter of the undercuttingguide 1734, as illustrated in FIG. 64.

The cutting head 1738 may be moved to the extended configuration, asillustrated in FIG. 65, where a length of the cutting extension 1744 isincreased to increase the area of the ilium and the sacrum that may beprepared for the sacroiliac fusion.

The number of sections in the cutting extension 1744 may be selectedbased upon the surface area that must be prepared for the sacroiliacfusion. A variety of techniques may be used for moving the sections ofthe cutting extension 1744 between the retracted and extendedconfigurations. An example of one such suitable technique is hydraulics.

Another embodiment of the cutting assembly 1832 includes a rotatablecutting head 1838, as illustrated in FIG. 66. The cutting head 1838 ismounted to a distal end of a support shaft 1834.

The cutting head 1838 has a generally circular shape and includes acutting element 1842 on an outer surface thereof. The cutting elements1842 may take a variety of configurations. One suitable configurationfor the cutting elements 1842 is a flexible material that is adjacent tothe surface of the cutting head 1838 when the cutting head 1838 is notrotated. Rotation of the cutting head 1838 may cause the cuttingelements 1842 to extend outwardly.

To increase an area that is prepared with the cutting assembly 1832, thecutting head 1838 may be rotatable about an axis 1850 that is offsetfrom a central axis of the support shaft 1834, as illustrated in FIGS.67-69. A series of cutting heads 1838 with progressively offset axes1850 may be used to progressively increase the area that is prepared bymoving the rotational axis 1844 closer to an edge of the cutting head1838, as illustrated by the difference between FIGS. 68 and 69.

Another configuration of the cutting assembly 1932 is illustrated inFIGS. 70 and 71. The cutting assembly 1932 may include an undercuttingguide 1934 in which a cutting head 1938 is mounted.

The cutting head 1938 may include a base portion 1940 and a cuttingportion 1942 that extends from a distal end of the base portion 1940 inan orientation that is generally perpendicular to the orientation of thebase portion 1940. A distal end of the base portion 1940 may be angledto facilitate urging the cutting head 1938 from a refractedconfiguration (FIG. 70) to an extended configuration (FIG. 71). Thecutting head 1938 may be biased to the retracted configuration.

The cutting portion 1942 may include a cutting surface on the upper andlower edges 1950, 1952 thereof. The cutting portion 1942 may also have acutting surface on an outer edge 1954 thereof. The cutting surface maytake a variety of configurations such as is discussed above with respectto the other configurations of the cutting assembly.

The cutting assembly 1932 may also include a biasing element 1944 withan angled distal surface 1646. When the biasing element 1944 is urgedtoward the distal end of the cutting assembly 1932, the angled distalsurface 1846 engages the distal end of the base portion 1940 to causethe cutting head 1938 to move from the retracted configuration to theextended configuration. While it is not necessary for the angle oforientation of the two angled surfaces to be the same, the angledsurfaces should be generally oriented in the same direction.

Once the cutting head 1938 is in the extended configuration, the cuttingassembly 1932 may be rotated to remove tissue from between the ilium andthe sacrum. After the tissue is removed, the biasing element 1944 may bemoved toward the proximal end of the cutting assembly 1932. Suchmovement allows the cutting head 1938 to move from the extendedconfiguration to the retracted configuration. Thereafter, the cuttingassembly 1932 may be removed.

Another configuration of the cutting assembly 2032 includes a linkageassembly having a plurality of arm sections 2040 that are pivotallymounted with respect to each other, as illustrated in FIGS. 72 and 73.The cutting assembly 2032 is mounted within an undercutting guide 2034.

The linkage assembly causes the cutting head 2038 to pivot from aretracted configuration (FIG. 72) to an extended configuration (FIG.73). Similar to the other configurations of the cutting assembly, thecutting head 2038 may include cutting surfaces on the upper, lower andend edges thereof.

Another configuration of the cutting assembly 2132 includes a pre-bentsharpened loop 2138 that is attached to a control rod 2140, asillustrated in FIGS. 74 and 75. The control rod 2140 is slidably mountedin an outer tube 2142. The outer tube 2142 has an opening formed thereinproximate a distal end thereof. The opening is configured to allow thepre-bent sharpened loop 2138 to extend therefrom.

In an initial configuration, the pre-bent sharpened loop 2138 issubstantially retained within the control rod 2140 so that the cuttingassembly 2132 may be inserted into the cannula 2134.

Once the distal end of the cutting assembly 2132 is positioned betweenthe ilium and the sacrum, the pre-bent sharpened loop 2138 may beprogressively extended from the outer tube 2142. Extension andretraction of the pre-bent sharpened loop 2138 may be controlled using avariety of techniques. In one technique, the control rod 2140 slideswith respect to the outer tube 2142 such that sliding of the control rod2140 causes the pre-bent sharpened loop 2138 to slide.

As an alternative to advancing both ends of the pre-bent sharpened loop2138 at the same rate, it is possible to advance only one of the ends ofthe pre-bent sharpened loop 2138 when moving the cutting assembly 2132from the retracted configuration to the extended configuration.

If a distal end of the cutting assembly 2132 engages a surface that thecutting assembly 2132 cannot cut through and the operator continues torotate the cutting assembly 2132, it is possible that the cuttingassembly 2132 may break. Breakage of the cutting assembly 2132 whenpositioned between the ilium and the sacrum may present challenges tothe extraction of the components of the cutting assembly 2132 throughthe cannula. For example, it may be necessary for a larger aperture tobe formed in the ilium to extract the broken components. Such a largeraperture would negatively impact the patient's ability to recover fromthe surgery.

To minimize the potential of the cutting assembly 2132 breaking duringthe cutting process, a clutch mechanism may be provided between thehandle and the cutting assembly 2132. The clutch mechanism causes theoperable connection between the handle and the cutting assembly 2132 torelease when greater than a threshold force is encountered. When thisoccurs, the handle rotates with respect to the cutting assembly 2132.

An audible notification may be provided to indicate to the personoperating the cutting assembly 2132 that the clutch has been engaged. Anexample of which such audible notification is a scratching sound that issufficiently loud to be heard outside of the patient.

After the clutch has been activated, the person operating the cuttingassembly 1832 may rotate the cutting assembly 2132 in an oppositedirection or partially retract the cutting assembly 2132. Thereafter,the cutting process may be resumed.

Another configuration of the undercutting system is illustrated in FIGS.76-81. A feature of this undercutting system is that it includes adetachable cutting assembly 2232. The detachable cutting assembly 2232enables the undercutting system to be reconfigured for different aspectsof preparing the surfaces of the ilium and the sacrum for the sacroiliacfusion process. The detachable cutting assembly 2232 may also bereplaced if it becomes dull or damaged in use.

The undercutting system includes an outer shaft 2234 positioned withrespect to a rotation handle 2272. Rotating the rotation handle mayrotate the undercutting system. An advancement handle 2236 is positionedin the proximal end of the rotation handle 2272. Rotating theadvancement handle 2236 enables external threads 2274 on the advancementhandle 2236 to interface with the internal threads 2276 on the rotationhandle 2272 permitting attachment and variable position adjustment ofthe advancement handle 2236 with respect to the rotation handle 2272 andouter shaft 2234.

The cutting assembly guide 2230 may have a distal portion with adiameter that is approximately the same as an outer diameter of theouter shaft 2234, while the proximal portion has a diameter that isapproximately the same as the inner diameter of the outer shaft 2234.Using such a configuration enables a proximal portion of the cuttingassembly guide 2230 to be inserted into the outer shaft 2234 untilreaching the stepped shoulder on the distal portion of the cuttingassembly guide 2230.

The cutting assembly guide 2230 has a channel 2240 extendingtherethrough. The channel 2240 may have a height and a width that areboth slightly larger than a height and a width of the cutting assembly2232. Using such a configuration enables the cutting assembly 2232 toslide with respect to the cutting assembly guide 2230.

The channel 2240 includes a proximal channel portion 2242 and a distalchannel portion 2244 that are in communication with each other. Theproximal channel portion 2242 may be generally aligned with a centralaxis of the cutting assembly guide 2230 while being offset along asurface of the cutting assembly guide 2230. In such a configuration, theouter shaft 2234 extends over the open edge of the proximal channelportion 2242 to thereby retain the cutting assembly 2232.

The distal channel portion 2244 is curved to change from an orientationgenerally parallel to the central axis of the cutting assembly guide2230 to an orientation generally perpendicular to the central axis. Thedistal channel portion 2244 thereby deflects the cutting assembly 2232to an orientation such that the cutting assembly can extend between theilium and the sacrum to remove cartilage therefrom.

The radius of curvature of the distal channel portion 2244 depends onthe space available and the flexibility of the cutting assembly 2232. Ifthe cutting assembly 2232 is highly flexible, the radius can berelatively small. On the other hand, if the cutting assembly 2232 isless flexible, the radius will need to be larger.

A variety of techniques may be used for connecting the cutting assembly2232 to an advancement handle 2236 on the outside of the undercuttingsystem to enable the cutting assembly 2232 to move from a retractedposition to an extended position. One suitable connection mechanismutilizes a connector head 2252. The connector head 2252 may or may notbe permanently attached to the advancement handle 2236 or the cuttingassembly 2232.

In one configuration, the connector head 2252 includes a ball mechanism2254 extending from an end thereof. The advancement handle 2236 has aball shaped recess 2256 formed therein. The ball mechanism 2254 may havea diameter that is slightly smaller than a diameter of the ball shapedrecess 2256.

The ball mechanism 2254 may be placed in the ball shaped recess 2256from a side thereof. Using such a configuration enables the connectorhead 2252 to be detached from the advancement handle 2236 when the ballmechanism 2254 and the ball shaped recess 2256 are not in the outershaft 2234. When the ball mechanism 2254 and the ball shaped recess 2256are both within the outer shaft 2234, the connector head 2252 isretained in engagement with the advancement handle 2236.

The use of the preceding mechanism for operably attaching theadvancement handle 2236 and the connector head 2252 enables theadvancement handle 2236 to rotate with respect to the connector head2252 without the connector head 2252 rotating.

An end of the connector head 2252 opposite the ball mechanism 2254 mayinclude a recess 2260 that is adapted to receive a portion of thecutting assembly 2232 for operably attaching the cutting assembly 2232to the connector head 2252.

In certain embodiments, the connector head 2252 has a pin 2262 extendingtherefrom and an aperture 2264 is formed in an end of the cuttingassembly 2232. This configuration operably connects the cutting assembly2232 and the connector head 2252 when these components are in the outershaft 2234.

The connector head 2252 may have a generally cylindrical shape with anouter diameter that is slightly smaller than an inner diameter of theouter shaft 2234 so that the connector head 2252 may be positionedwithin the outer shaft 2234.

A proximal end of the advancement handle 2236 may have a grippingsurface 2270 formed thereon to enhances the ability of the operator tomanipulate the advancement handle 2236. The gripping surface 2270 mayhave a variety of surface textures and a diameter greater than thedistal diameter of the advancement handle 2236.

A distal end of the advancement handle 2236 may have a generallycylindrical shape that is slightly smaller than an inner diameter of theouter shaft 2234 so that it may be positioned within the outer shaft2234.

A rotation handle 2272 may be positioned over a proximal end of theouter shaft 2134. The rotation handle 2272 may have a diameter that isgreater than a diameter of the gripping surface 2270 of the advancementhandle 2236. Forming these surfaces with different diameters reduces thepotential of the operator engaging both of the surfaces when it isintended to grip only one of the surfaces.

The rotation handle 2272 may be used for rotating the undercuttingsystem once the undercutting system is moved to an extended positionbetween the ilium and the sacrum. Increasing the diameter of therotation handle 2272 thereby increases the torque that may be applied tocause the undercutting system to cut through the cartilage between theilium and the sacrum.

A torque limiting device may be included in the components of theundercutting system. The torque limiting device may protect the cuttingassembly 2232 from breaking in response to a sufficiently largerotational force being placed on the cutting assembly 2232. A person ofskill in the art will appreciate that the torque limiting device maytake a variety of configurations.

The undercutting system may also include an auto advancing system thatcauses the advancement handle 2236 to advance automatically in responseto rotation of the rotation handle 2272. This would cause the cuttinghead to move further into the region between the ilium and the sacrum inresponse to rotation of the undercutting system. A person of skill inthe art will appreciate that a variety of techniques may be used tofabricate the auto advancing system.

The cutting assembly 2232 may be formed with a round or square profilethat conforms to the profile of the channel 2240. The cutting assembly2232 may include a tip portion 12280 having at least one sharpened edge.

Such a configuration provides the tip portion 2280 with flexibilityalong a distal-proximal direction while providing the tip portion 2280with rigidity along a radial-tangential direction. The distal-proximalflexibility enables the cutting assembly 2232 to conform to surfaces ofthe ilium and the sacrum that are not flat and/or perpendicular to theaxis of the undercutting system. The radial-tangential rigidity enablesthe cutting assembly 2232 to cut cartilage as the undercutting system isrotated.

A length of the tip portion 2280 may be selected based upon a size ofthe ilium and the sacrum that must be prepared by removing the cartilagefrom therebetween. Minimizing the length of the tip portion 2280 may bedesirable to reduce the cost of the cutting assembly 2232, as the tipportion 2280 may be more expensive than the other portions of thecutting assembly 2232.

An end 2282 of the tip portion 2280 may not include a sharpened surface.Forming the end 2282 with such a configuration reduces the potential ofundesirable cutting as the cutting assembly 2232 is being inserted intothe region between the ilium and the sacrum. As illustrated in FIG. 80,the end 2282 may be curved such as in a semi-circular shape.

The tip portion 2280 may have an oscillating configuration that is atleast partially in a sinusoidal shape. A variety of techniques may beused to fabricate the cutting assembly 2232 with such a shape. Forexample, the loops may be cut into a straight piece of material.Alternatively, a straight piece of material may be bent to form theloops. The material from which the cutting assembly is fabricated mayplay a role in determining the technique used to fabricate the cuttingassembly 2232. Suitable materials for the cutting assembly 2232 mayinclude stainless steel, nitinol, and elgiloy.

Another configuration of the undercutting system is illustrated in FIG.82. This embodiment of the undercutting system is similar to theembodiment illustrated in FIGS. 76-81 except that an end of the cuttinghead 2336 is outwardly directed. Such a configuration may assist informing an initial hole in the cartilage prior to rotation of theundercutting system.

Another configuration of the undercutting system is illustrated in FIG.83. This embodiment of the undercutting system is similar to theembodiment illustrated in FIGS. 76-81 except that an end of the cuttinghead 2436 is in the shape of a loop and a portion of the cutting head2336 extends behind the oscillating portion of the cutting head 2436.This configuration may provide additional rigidity to the cutting head2436 when rotating to cut the cartilage between the ilium and thesacrum.

Another configuration of the undercutting system is illustrated in FIGS.84-86. This embodiment includes an undercutting guide similar to theembodiment illustrated in FIGS. 76-81. The cutting assembly 2532 isformed from a relatively rigid wire such as nitinol.

A cutting cap 2540 is attached to a distal end of the wire. The cuttingcap 2540 may have a relatively smooth curved distal surface, asillustrated in FIG. 85. A proximal surface of the cap may include asharpened edge 2542.

Using this configuration of the undercutting system, the wire could bepushed and rotated to advance the cutting cap. Rotation of theundercutting system causes the sharpened edge 2542 to engage and cut thecartilage. During this rotating process, the wire may bend asillustrated in FIG. 86. Such a bending motion enhances the ability ofthe sharpened edge to cut the cartilage.

Another configuration of the undercutting system involves forming twooffset apertures 2602, 2604 in the ilium, as illustrated in FIG. 87. Theapertures 2602, 2604 partially overlap such that the apertures form anoblong aperture. The oblong aperture is adapted to receive a similarlyshaped oblong cannula 2614. The oblong aperture is also adapted toreceive an undercutting system having a shaft 2610 with a cutting head2612 extending laterally there from, as illustrated in FIG. 88.

This configuration of the undercutting system enables the cutting head2612 to be either fixedly mounted or partially advanced from the shaft2610 so to minimize issues with the cutting head 2612 advancement withrespect to the shaft 2610. As the shaft 2610 is rotated, it may benecessary to move a rotational axis of the shaft 2610 from one side ofthe oblong cannula 2614 to another, so that the inner surface of theilium all around the aperture 2602, 2604 is prepared for the sacroiliacfusion.

Depending on a thickness of the cutting head 2612, it may be necessaryto move the shaft axially so that an upper end of the cutting head 2612contacts the inner surface of the sacrum to prepare that surface for thesacroiliac fusion.

In operation, after appropriate preparation of the patient andidentification of the location for the sacroiliac fusion, at least oneaperture 2810 is drilled through the ilium 14 and at least partiallyinto the sacrum 16, as illustrated in FIG. 89. In certain embodiments,there are three apertures drilled.

A conventional surgical drill 2812 and drill bit 2814 may be utilized toform the aperture 2810. The aperture 2810 may be formed with a diameterthat is selected based upon a diameter of the bone screw 2820 that willbe inserted into the aperture 2810 as part of the sacroiliac fusionprocess.

Next, the undercutting system 2830 is positioned in a retractedconfiguration so that the cutting assembly 2832 does not interfere withthe insertion process. The distal end of the undercutting system 2830 isextended into the aperture 2810, as illustrated in FIG. 90.

Once the distal end of the undercutting system 2830 is positionedbetween the ilium 14 and the sacrum 16, as illustrated in FIG. 91, thecutting assembly 2832 is moved to an at least partially extendedconfiguration. The undercutting system 2830 is rotated to causecartilage between the ilium 14 and the sacrum 16 that is in the path ofthe cutting assembly 2832 to be cut up.

Contact between the cutting assembly 2832 and the inner surfaces of theilium 14 and the sacrum 16 causes the respective surfaces to be abradedto create bleeding bone, which is needed to facilitate bone growthbetween the ilium 14 and the sacrum 16 as part of the sacroiliac fusionprocess.

A technique is then utilized to remove the bits of cartilage and othertissue from between the ilium 14 and the sacrum 16. One suitableapparatus that may be used for remove the bits of cartilage and othertissue is a radial deployment surgical tool, which is described in U.S.Applic. No. 61/349,303, which was filed with the U.S. Patent & TrademarkOffice on May 28, 2010, and which is assigned to the assignee of thepresent patent application.

Thereafter, bone screws 2820 may be inserted into each of the apertures2810, as illustrated in FIG. 92. The bone screws 2820 will be effectiveat maintaining the ilium 14 and the sacrum 16 in a stationary positionwith respect to each other as bone grows there between to cause fusionof the ilium 14 and the sacrum 16.

While the figures only illustrated the procedure being performed on oneside of the patient, a person of skill in the art will appreciate thatthe process may be repeated on the other side of the patient.

Depending on a variety of factors such as the sharpness of the cuttinghead and the hardness of the material being cut, it may not be possibleto merely cut through the cartilage and bone using just a rotationalmotion. Rather, it may be necessary to alternate rotate the undercuttingsystem in clockwise and counter clockwise directions to increase thearea that is prepared. While in many circumstances, it may be desirableto prepare a circular area, it is also possible to use the concepts ofthe invention to prepare a semi-circular area.

A variety of techniques may be used to evaluate the amount of cartilagethat has been removed and the extent to which the surfaces of the iliumand the sacrum have been prepared. Examples of such suitable techniquesinclude monitoring the sound emitted during the cutting process, as thecutting of bone may make a scraping sound.

The person operating the undercutting system may monitor the performanceof the process using the feel of the cutting head, as it may be moredifficult for the cutting head to cut through the ilium and the sacrumthan the cartilage.

It is also possible to monitor the progress of the preparation for thesacroiliac fusion using a fluoroscope. While these techniques aredescribed individually, it is possible for one or more of the precedingtechniques to be combined.

After a desired amount of cartilage between the ilium and the sacrum hasbeen cut up to prepare for the sacroiliac fusion, it may be desirable toremove the cut up bits of cartilage from between the ilium and thesacrum to facilitate bone growth between the ilium and the sacrum.

One technique for removing the cut up bits of cartilage is to flush theregion with a fluid and then suction out the water with the cut up bitsof cartilage. The process may be repeated until a desired amount of thecut up bits of cartilage is removed from between the ilium and thesacrum.

Another technique for removing the cut up bits of cartilage from betweenthe ilium and the sacrum involves using a clean-up tool. The clean-uptool may include a handle and a plurality of bristles.

After the surfaces of the ilium and the sacrum have been prepared, abone graft may be inserted. Then, a variety of techniques may be used tomaintain the ilium and the sacrum in a fixed position with respect toeach other. Examples of suitable fixation techniques include bonescrews, cannulated screws, pins, cages, glue, coupled device with balland socket and Herbert screws.

While the concepts of the invention are primarily described inconjunction with preparation for a sacroiliac fusion, a person of skillin the art will appreciate that the concepts may be adapted for otherjoints in the body. The concepts may also be used for preparing aninterior region of a bone.

In the preceding detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thepreceding detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is contemplated that features disclosed in this application, as wellas those described in the above applications incorporated by reference,can be mixed and matched to suit particular circumstances. Various othermodifications and changes will be apparent to those of ordinary skill.

The invention claimed is:
 1. An undercutting system for preparing aregion between an ilium and a sacrum for sacroiliac fusion, wherein theundercutting system comprises: an insertion apparatus having an elongateshaft and a rotatable handle; and a cutting assembly operably attachedto the insertion apparatus, wherein rotation of the handle with respectto the shaft causes the cutting assembly to move with respect to theshaft between a retracted configuration and an extended configurationand wherein in the extended configuration, at least a portion of thecutting assembly extends laterally from the shaft.
 2. The undercuttingsystem of claim 1, wherein the insertion apparatus comprises anelongated shaft and a handle extending therefrom opposite the cuttingassembly.
 3. The undercutting system of claim 1, wherein the cuttingassembly has a cutting surface on at least one edge thereof.
 4. Theundercutting system of claim 1, wherein the cutting assembly has a firstside and a second side that is oriented opposite the first side, whereina cutting surface is provided on the first side and the second side. 5.The undercutting system of claim 4, wherein the first side and thesecond side are each defined by a first edge, a second edge and a thirdedge that extends between the first edge and the second edge oppositethe insertion apparatus, wherein the cutting surface is provided on thefirst edge and the second edge and wherein the cutting surface is notprovided on the third edge.
 6. The undercutting system of claim 5,wherein the third edge has a guide tip extending therefrom.
 7. Theundercutting system of claim 1, wherein the cutting assembly resistsmovement in a radial direction with respect to the insertion apparatus.8. The undercutting system of claim 1, wherein the cutting assemblyexhibits flexibility in a distal-proximal direction with respect to theinsertion apparatus.
 9. The undercutting system of claim 1, wherein thecutting assembly is rotatably mounted to the insertion apparatus,wherein the distal end of the insertion apparatus has a width andwherein the cutting assembly is substantially within the width when thecutting assembly is in the refracted configuration.
 10. The undercuttingsystem of claim 9, wherein the cutting assembly is rotatable about anaxis that is parallel and offset from the central axis of the insertionapparatus.
 11. The undercutting system of claim 9, wherein the cuttingassembly is rotatable about an axis that is substantially perpendicularto the central axis of the insertion apparatus.
 12. The undercuttingsystem of claim 1, and further comprising a cutting assembly lockingmechanism, wherein the cutting assembly locking mechanism is movablebetween a locked configuration and an unlocked configuration, whereinthe cutting assembly is retained in a stationary position with respectto the insertion apparatus when the cutting assembly lock mechanism isin the locked configuration and wherein the cutting assembly is movablewith respect to the insertion apparatus when the cutting assembly lockmechanism is in the unlocked configuration.
 13. The undercutting systemof claim 12, wherein the insertion apparatus includes at least onerecess formed therein and wherein the cutting assembly locking mechanismengages the insertion apparatus proximate the at least one recess whenin the locked configuration.
 14. The undercutting system of claim 13,wherein the at least one recess comprises a plurality of recesses thatare arranged in a semi-circular configuration.
 15. The undercuttingsystem of claim 12, wherein the locking mechanism is operably connectedto the cutting assembly with a shaft and wherein the shaft extendsthrough the insertion assembly.
 16. The undercutting system of claim 1,wherein at least a portion of the cutting assembly telescopes toincrease a length of the cutting assembly.
 17. The undercutting systemof claim 1, wherein the cutting assembly is slidably mounted to theinsertion apparatus, wherein the distal end of the insertion apparatushas an aperture formed therein, wherein the cutting assembly issubstantially within the aperture when the cutting assembly is in theretracted configuration.
 18. The undercutting system of claim 1, whereinthe insertion apparatus comprises a guide channel extending between theproximal end and the distal end thereof.
 19. The undercutting system ofclaim 18, wherein proximate the proximal end the guide channel isaligned substantially parallel to the central axis of the insertionapparatus, wherein proximate the distal end the guide channel issubstantially transverse to the central axis and wherein intermediatethe proximal end and the distal end the guide channel comprises atransition region.
 20. The undercutting system of claim 1, wherein thecutting assembly cuts using a reciprocating motion moving the cuttingassembly towards and away from the distal end of the insertion assembly.21. The undercutting system of claim 1, wherein the cutting assemblycomprises a plurality of links that are pivotally mounted to each other,wherein a cutting surface is formed on an edge of at least one of theplurality of links.
 22. The undercutting system of claim 1, wherein atleast a portion of the cutting assembly has a plurality of bristlesextending from an outer surface thereof.
 23. The undercutting system ofclaim 1, wherein the cutting assembly comprises a plurality of cuttingarms that are deflectable from a retracted configuration where thecutting arms are substantially parallel to a central axis of theinsertion assembly to an extended configuration where at least a portionof the cutting arms are substantially perpendicular to the central axisof the insertion assembly.
 24. The undercutting system of claim 23, andfurther comprising a deflector mechanism that is operably connected tothe insertion assembly for deflecting the cutting arms from theretracted configuration to the extended configuration.
 25. Theundercutting system of claim 1, wherein cutting assembly comprises aplurality of slits formed therein that define a plurality of cuttingarms, the plurality of slits are proximate to but do not extend all ofthe way to the distal end of the cutting assembly.
 26. The undercuttingsystem of claim 24, wherein the cutting assembly is moveable to aretracted configuration where at least a portion of the cutting armsbows outwards from a central axis of the cutting assembly.
 27. Theundercutting system of claim 1, wherein the cutting assembly comprises:a shaft having a distal end; and a cutting head extending radially fromthe shaft proximate the distal end of the shaft.
 28. The undercuttingsystem of claim 1, wherein the cutting assembly comprises: a cuttinghead rotatably mounted to the insertion assembly for rotation about anaxis that is substantially parallel to the central axis of the insertionassembly; and a plurality of cutting elements operably connected to anouter surface of the cutting head.
 29. The undercutting system of claim1, wherein the cutting assembly comprises: a cutting portion operablymounted with respect to the insertion assembly for movement between aretracted configuration and an extended configuration; and a biasingelement for urging the cutting portion from the retracted configurationto the extended configuration.
 30. The undercutting system of claim 29,wherein the biasing element is slidable along an axis that issubstantially parallel to the central axis of the insertion assembly andwherein the cutting portion is slidable along an axis that issubstantially perpendicular to the central axis of the insertionassembly.
 31. The undercutting system of claim 1, wherein the insertionapparatus further comprises a control portion operably attached theretoproximate a proximal end thereof.
 32. The undercutting system of claim31, wherein the control portion is operably attached to the cuttingassembly for moving the cutting assembly between the extendedconfiguration and the retracted configuration.
 33. The undercuttingsystem of claim 1, wherein the insertion apparatus has at least onechannel formed therein that extends from the proximal end to the distalend thereof and wherein the channel may be used for delivering a fluidor a gas and removing the fluid or the gas from proximate the cuttingassembly.
 34. The undercutting system of claim 1, wherein the cuttingassembly comprises a linkage assembly that is operably connected to acutting head and wherein the linkage assembly comprises a plurality ofarm sections that are pivotally mounted with respect to each other. 35.The undercutting system of claim 1, wherein the cutting assemblycomprises a cutting head and a control rod that is operably connected tothe cutting head, wherein urging the control rod causes the cutting headto extend through an aperture in the insertion assembly and deflect toan orientation substantially perpendicular to a central axis of theinsertion assembly.
 36. The undercutting system of claim 35, wherein thecutting head is operably attached to the control rod with a clutchmechanism.
 37. The undercutting system of claim 36, wherein the clutchmechanism provides an audible notification of being engaged.
 38. Theundercutting system of claim 1, wherein the cutting assembly comprises:an advancement handle; and a cutting head assembly detachably mounted tothe advancement handle.
 39. The undercutting system of claim 38, andfurther comprising a cutting assembly guide to direct the cutting headassembly to an orientation that is substantially perpendicular to acentral axis of the insertion assembly, wherein the cutting assemblyguide has a channel formed therein.
 40. The undercutting system of claim38, wherein the cutting head assembly is fabricated from a flexiblematerial that is oriented in an oscillating shape.
 41. An undercuttingsystem for preparing a region between an ilium and a sacrum forsacroiliac fusion, wherein the undercutting system comprises: aninsertion apparatus comprising a guide shaft having a distal end,wherein the guide shaft is oriented about a central axis and wherein aradius of the guide shaft extends between the central axis and an outersurface of the guide shaft; and a cutting assembly having a cuttingsurface, wherein the cutting assembly exhibits flexibility in adistal-proximal direction with respect to the insertion apparatus,wherein the cutting assembly is slidably mounted with respect to theinsertion apparatus for movement between a retracted configuration andan extended configuration, wherein when the distal end of the cuttingassembly is extended beyond the distal end of the guide shaft, thecutting surface can engage tissue between the ilium and the sacrum thatis at a distance from the central axis of the guide shaft that isgreater than the radius of the guide shaft.
 42. The undercutting systemof claim 41, wherein the cutting surface is located proximate the distalend of the cutting assembly.
 43. The undercutting system of claim 41,wherein the cutting assembly is rotatable with respect to the guideshaft.
 44. The undercutting system of claim 41, wherein the cuttingassembly comprises an elongated shaft and a cutting head that isattached to a distal end of the elongated shaft and wherein the cuttingsurface is provided on the cutting head.
 45. The undercutting system ofclaim 42, wherein the cutting assembly is movable between a retractedconfiguration and an extended configuration, wherein when the cuttingassembly is in the retracted configuration, the cutting assembly iswithin a diameter of the guide shaft and wherein when the cuttingassembly is in the extended configuration, the cutting assembly extendsbeyond the diameter of the guide shaft.